The present invention relates to ball valves and, more particularly, to a ball valve for use in an oil and gas production system and specifically within a tubing hanger of a production tree.
The oil and gas production industry has historically relied upon gate valves for controlling fluid flow. Ball valves are, of course, widely used in other industries, e.g., in piping systems for handling various fluids. Ball valves have occasionally been used in the oil and gas production industry, but a ball valve is generally not considered as reliable as a gate valve due to concerns regarding reliable sealing between the seats and one or more of the valve body, the valve actuator, and/or the ball. Gate valves are, however, generally quite bulky and expensive compared to ball valves. In oil and gas production systems, the size of the valve is frequently a significant concern since the area around the production tree is limited, and the production tree includes numerous pieces of equipment, such as bulky gate valves, which must be reliably maintained and, if necessary, replaced.
Relevant prior art patents include Beazley, U.S. Pat. No. 5,313,979; Kemp, U.S. Pat. No. 4,911,408; Kemp, U.S. Pat. No. 4,899,980; Halpine, U.S. Pat. No. 4,113,231; Moran, U.S. Pat. No. 4,147,327; Scaramucci, U.S. Pat. No. 4,254,793; Mohrfeld, U.S. Pat. No. 4,815,700; Godfrey et al., U.S. Pat. No. 5,338,001; Milberger, et al., U.S. Pat. No. 4,317,490; Noack, et al., U.S. Pat. No. 5,551,665; Morgan, U.S. Pat. No. 5,575,336; and Muchow, 4,386,756. U.S. Pat. No. 6,293,513 discloses a ball valve having a convex seat. U.S. Pat. No. 6,176,316 discloses a subsea wellhead assembly with ball valves disposed within the vertical bores of the in-line tree assembly. U.S. Pat. No. 5,575,363 discloses a safety valve for use in a horizontal tree. The assembly includes a cylindrical spool supported for rotation about its longitudinal axis in the valve body. U.S. Pat. No. 4,415,037 discloses a ball valve assembly designed to eliminate tearing of the annular elastomeric seal which engages the periphery of the ball in response to excessive loading. U.K. Patent Application No. 2,358,207 discloses a subsea wellhead assembly using a pair of swab valves, a pair of control valves, a cross-over valve, and an annular master valve and another swab valve. Application WO 00/15943 discloses a ball valve intended to be offloaded from a valve seat during rotation. Application WO 01/53654 discloses a sleeve valve and a hydraulically actuated ball valve disposed in the annulus bore of a tubing hanger body.
The disadvantages of the prior art are overcome by the present invention, and an improved and relatively compact ball valve assembly is hereinafter disclosed which has particular utility in an oil and gas production system.
The ball valve assembly includes a valve body having an inlet port, an outlet port, a passageway between these ports for transmitting fluid, an open valve hydraulic port and a closed valve hydraulic port. A ball positioned within the valve body has a throughport therein and it is rotated between the open and closed position in response to axial movement of an actuator sleeve which surrounds the ball and is moveably responsive to hydraulic pressure in one of the hydraulic ports. A seat ring within the valve body seals with the spherical exterior surface of the ball when the ball is closed and fluid pressure is upstream or downstream of the ball. A support ring engages the exterior surface of the ball and supports the ball when fluid pressure is upstream of the ball.
A particular feature of the invention is to provide the ball valve assembly with a first seal between the seat ring and the actuator sleeve, a second seal between the support ring and the actuator sleeve, a third sleeve seal between the actuator sleeve and the valve body, a fourth seal between the seat ring and the valve body, and a fifth seal between the support ring and valve body. The first seal and the fourth seal are sized such that the pressure within the seat ring exerts an axially directed force on the seat ring which is transmitted to the ball. A related feature of the invention is that each of the seat ring and support ring has a substantially spherical ball engaging concave surface for mating engagement with the exterior surface of the ball. Each of the seat ring and support ring preferably also includes an inner convex surface spaced between the ball engaging surface and the inner diameter of the ring, and an outer convex radius surface spaced between the ball engaging surface and the outer diameter of the ring. The concave radius surface on the seat ring provides low pressure sealing with the ball and the inner convex radius surface on the seat ring provides high pressure sealing when the seat ring diameter increases.
A significant feature of the invention is that the actuator sleeve surrounds the ball and is axially moveable within the valve body for rotating the ball between the open position and the closed position, with hydraulic pressure in at least one hydraulic port moving the actuator sleeve within the valve body. The support ring which engages the exterior surface of a ball when the ball is in the closed position and supports the ball when the fluid pressure is upstream from the ball is prevented from sealing engagement of the ball and the support ring. The fluid passageway for preventing sealing engagement of the ball and the support ring may be provided in either the ball or the support ring. The actuating sleeve is continuous between an upper end above the ball and a lower end below the ball, such that the actuator sleeve maintains fluid pressure within the valve body when the ball is in the open position.
As a further feature of the invention, both the ball and the ball engaging ring are preferably formed from a high strength material, while the seat ring is formed from a low strength material. A high strength coating may be provided on surfaces of the seat ring which provide sealing engagement with the ball. A seat ring may be formed from steel, stainless steel, a nickel-base material, a titanium-base material or a beryllium copper material, while the ball and the ball engaging ring of the support ring may be formed from a ceramic material or a tungsten carbide material.
Yet another feature of the invention is that the ball includes radially opposing flats for cooperation with corresponding flats on the actuator sleeve. A pair of opposing pin members each extending between a flat on the ball and a corresponding flat on the actuator sleeve are positioning within a slot in the ball and a corresponding hole in the actuator sleeve to rotate the ball between the open position and the closed position in response to axial movement of actuator sleeve.
A feature of the invention is that seals that seal both bore pressure and hydraulic fluid pressure include a plurality of axially spaced sealing elements, with softer seal elements near fluid pressure and harder seal elements downstream from fluid pressure. A related feature of the invention is that each of these seals are bi-directional seals.
The seals which engage the seat ring cause the seat ring to move toward the ball in response to hydraulic fluid pressure within the interior of seat ring, while the seals which engage the support ring do not result in significant force pressing the support ring toward the ball when fluid pressure is interior of the support ring.
Another feature of the invention is that each of the seat ring and support ring has a wall thickness from 0.3 to 0.6 times the radius of the bore through the respective ring.
A further feature of the invention is that energizer springs may be used for urging the seat ring and the support ring, respectively, toward the ball.
Yet another feature of the invention is that the actuator sleeve supports a plurality of axially spaced guide rings to minimize contact between the actuator sleeve and the valve body.
Still a further feature of the invention is that the valve body is provided with both an open valve hydraulic port and a closed valve hydraulic port for axially moving the actuator sleeve, and the seat ring maintains hydraulic pressure exterior of the seat ring and the support ring maintains hydraulic pressure exterior of the support ring.
A further feature of the invention is that the support ring may comprise a ball engaging ring for engaging the exterior surface of the ball, and a dissimilar material seal ring spaced opposite the ball with respect to the ball engaging ring. A juncture of the ball engaging ring and the seal ring need not provide sealing integrity since the seal between the actuator sleeve and the seal ring is spaced opposite the ball with respect to the juncture between the dissimilar materials of the support ring.
A further feature of the invention is that a vent hole in the ball may be provided for venting pressure from the exterior cylindrical surface of the ball to the through port in the ball. A vent hole may also be provided in each of the pin members which interconnect the actuator sleeve to the ball.
A further feature of the invention is that the pin members which interconnect the ball to the actuator sleeve are constructed so that rotation of each pin member with respect to the ball is restricted, so that the pin members and the ball rotate as an assembly with respect to the actuator sleeve during movement of the actuator sleeve.
Another feature of the invention is that the valve body may be a tubing hanger for supporting a tubing string in a well. In alternate embodiments, the valve body is a manifold block or a downhole safety valve.
A significant advantage of the present invention is that the components of the ball valve are readily available, thereby allowing for the economical manufacture, use, and repair of the ball valve which has improved life and high reliability compared to prior art valves.
Another advantage of the present invention is that the valve body for the ball valve assembly may take on various configurations, such as the body of a tubing hanger, the body of downhole safety valve, or the body of a manifold.
These and further objects, features, and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings.